UCC - CONSTRUCTION CODE COMMUNICATOR
Volume 27, Number 3 – Fall 2015
Chimney Liner Requirement – Rehab
The Code Assistance Unit has received many questions regarding whether a chimney liner is
required when a furnace, boiler or water heater is replaced in a one- or two-family dwelling.
Replacing a furnace, boiler or water heater in an existing one- and two- family dwelling falls under
the Rehabilitation Subcode, NJAC 5:23-6; this work is typically classified as “Renovation” by
definition. More specifically, NJAC 5:23-6.5(h) refers you to NJAC 5:23-6.8, the Residential
Materials and Methods. Here, you find that NJAC 5:23-6.8(h)14 requires compliance with all
portions of Chapter 24 from the 2009 International Residential Code (IRC) that pertains togas
equipment and there are many sections that refer to resizing chimneys when equipment is
replaced or removed.
A specific example from the IRC is Section G2425.15.1. Here it states, “The chimney or vent shall
be resized as necessary to control flue gas condensation in the interior of the chimney or vent
and to provide the appliance or appliances served with the required draft.”
The problem is there are no chimney or vent sizing tables that deal with exterior chimneys in the
IRC. Luckily, the International Code Council was smart enough to link the IRC to the 2009
International Fuel Gas Code (IFGC) in this manner. Here, Section G2401.1 of the IRC states in
the third paragraph, “The omission from this chapter of any material or method of installation
provided for in the International Fuel Gas Code shall not be constructed as prohibiting the use of
such material or method of installation. Fuel-gas piping systems, fuel-gas appliances and related
accessories, venting systems and combustion air configurations not specifically covered in these
chapters shall comply with the applicable provisions of the International Fuel Gas Code.”
Therefore, in order to resize the exterior chimney, Tables 504.3(6a) (6b) or 504.3 (7a) or (7b) in
the IFGC should be used.
When the contractor signs the “Chimney Verification” form, he/she is indicating that the existing
chimney is in good physical condition and is appropriately sized. When this form is submitted to
the construction office and the form indicates that there is an existing exterior chimney, that
should raise a flag that a chimney liner would be required.
Liner resizing is important due to equipment today being more efficient when it comes to exterior
chimneys. Less heat and draft up the chimney tend to cause a condensation problem.
Note that an interior chimney generally does not lead to a condensation problem because it is
located in a conditioned area.
Source: Thomas C. Pitcherello
Code Assistance Unit
(609) 984-7609